To help you avoid letting bad habits shine through at the worst moments, we asked experts to highlight some of the least professional behavior you could demonstrate that will almost certainly cost you a job.

Here's what you could be doing that makes you look unprofessional in your job search:

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Being sloppy

Your résumé is your first contact with HR or recruiters, Rosalinda Oropeza Randall, an etiquette and civility expert and the author of "Don't Burp in the Boardroom," tells Business Insider. And typos, grammar mistakes, and formatting issues will land it in the "no" pile within a few seconds.

"If your résumé is sloppy, they'll assume you are, too," she says.

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Not doing your homework

"Employers take note of candidates that are educated on the responsibilities of the job opening in question and on the company itself," Rosemary Haefner, chief human-resources officer for CareerBuilder, tells Business Insider. "This demonstrates that you made the decision to apply for the job after considering the facts, rather than out of desperation."

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Trying too hard to garner attention

If you want your résumé to stand out, for instance, "let it be because of its content and format," Randall says. "Using colored paper, a multitude of fonts, or even including confetti with your résumé will attract attention, but not the right kind."

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Skipping breakfast

As Lisa De Fazio, a healthy-lifestyle expert and registered dietitian, tells Business Insider, breakfast is the most important meal of the day.

By the time you wake up you likely haven't eaten for 10 or 12 hours, which is where breakfast got its name — it means "breaking the fast," De Fazio says.

When blood-sugar levels are low, she explains, it's much harder to focus and you're more likely to feel tired, irritable, and impatient, all of which make it impossible to do your best during an interview.

Smoking and drinking

"Your interviewer will smell it on you," she says. "If she's a smoker, she may not mind, but most interviewers gave up the nicotine habit."

Drinking before the interview is also a bad idea. While alcohol can help calm nerves, it does so by dulling the senses, Oliver says, and you run the risk of not sounding intelligent.

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Poor grooming and hygiene

Water shortage or not, if there's one occasion you really want to shower for, it's a job interview.

"Do you want people focusing on the musty odor that surrounds you or your brilliant words?" Randall asks. "Lack of effort in your appearance can be construed as potentially lacking effort in your work and work area."

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Being late

Frequent tardiness is a common bad habit, but do whatever you can to avoid showing up late to the interview.

It will tell the hiring manager that you are irresponsible, aren't taking this process seriously, and don't respect their time. And this is not the first impression you want to make.

Plan to arrive at least 15 minutes early. If you find yourself running way ahead of schedule, TopResume's career expert, Amanda Augustine, and Business Insider's director of talent, Stephanie Fogle, suggest killing time by ducking into a coffee shop or walking around the neighborhood

Why? Showing up too early isn't great, either. It can be frustrating for the hiring manager, as your early arrival could throw a curveball into their schedule.

Texting when bored

Texting while you wait will make you look as if you would rather be elsewhere, Oliver says.

Most waiting areas have magazines, Randall says, and if you see a company brochure, even better. Reading that will reflect your interest in the company.

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Grooming in public

Oliver says it's a good idea to pack a small grooming kit for a quick touch-up before an interview. But rather than apply lipstick or brush your hair in the reception area, you should arrive a few minutes before the interview starts, duck into the restroom, and complete your final grooming before the interview.

Bringing too much stuff

Your portfolio and copies of your résumé are all you need to bring to your interview — everything else is superfluous. Randall suggests leaving your latte or water bottle in the car and putting away your cell phone so you're free to shake hands.

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Dressing too casually

As they say, dress for the job you want, not the job you have.

"Sloppy clothes scream 'I don't care!' and are a surefire way to put off those around you," Randall says.

And dressing too formally for an interview can tell an employer that you didn't research the company culture and you're not a fit.

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Speaking without thinking

This is a terrible habit — and it can be especially detrimental during a job search.

Saying the wrong thing to the receptionist, for instance, can crush your chances of landing a job. Receptionists are often the first set of eyes and ears a company has, and what you say to them will probably make its way back to hiring managers.

Continually asking the receptionist if she is sure that your interviewer knows you're waiting for her out in the lobby may convey your neuroses, Oliver says. And flip comments like "Hey, beautiful," aren't the compliments you may think they are.

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Being too informal

"While I'm not promoting a formal, 'How do you do?'-style greeting, you might consider stepping it up a bit when you're introducing yourself to the person who will be determining whether you get the job or not," Randall says.

Leading with "Hey, what's up?" probably won't make the best first impression.

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Projecting a bad attitude

"If you doubt your abilities or see only the worst possible outcome, your interviewer might pick up on that negative energy," Haefner says.

"Similarly, it's important not to bad-mouth a former boss, coworker, or employee during any stage of the interview process," she says. "Even if your former boss or organization is known for its problems, a job interview is no time to express your anger."

Another bad attitude, arrogance, is often confused with confidence. Walk into the interview with a mix of confidence and humility, smile, and show some enthusiasm, Randall says.

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Being too demanding

Asking questions is an important part of the interview process — it shows you're engaged in the discussion and can help you determine if the job and company are a fit for you.

But while questions like, "What might I expect in a typical day?" and "How do you measure success?" show you to be invested in the opportunity, making certain requests before you even have the job makes you look more high-maintenance.

Randall suggests steering clear of queries like, "Can I sit by a window? It helps with my hourly meditation."

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Oversharing

"Naturally, the purpose of an interview is to impress the company with your talent and skills," Randall says. "But be aware of oversharing; they may learn more about you than they need to."

To avoid oversharing, she suggests following a few simple rules: Keep it relevant. Leave your childhood out of it. Don't insist on special favors or accommodations. And don't use the term "deal breaker."

Instead, listen and give the interviewer an opportunity to ask questions.

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Displaying shyness

It's understandable to be nervous during an interview, but you want to make sure you give interviewers more to go on than one-word or rushed answers.

Interviews, which generally involve a lot of talking about oneself, can be especially trying for shy people, and the unfortunate reality is that shyness is sometimes misconstrued as insecurity and even incompetence.

In a previous Business Insider story, Harvard Business School professor Amy Cuddy suggested taking your time to answer a question, which shows that you're taking the other person seriously and conveys a sense of power.

"When someone asks you a question," she said, "trust that they really want you to answer it thoughtfully. So don't even be afraid to pause before you answer it. Reflect; don't jump right in."

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Swearing

You may be really excited to be interviewing with your top choice for employer, but blurting out foul language is a surefire way to cut the interview short.

Swearing demonstrates to others that you aren't able to calmly and thoughtfully deal with a situation, Randall says.

"Using foul words or questionable language is not only a bad habit, but in most places of business, it's still considered unprofessional and can even land you in Human Resources for a little chat," Randall says.

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Interrupting

"It's rude to interrupt. When you do, it shows others that you don't have any respect, judgment, or patience," Randall says.

While participation can earn you some brownie points, bad timing can wipe those points away.

Poor body language

"What you say in an interview is as important as how you say it, and bad body language takes away from your words," Haefner says.

In a recent CareerBuilder survey, employers said that some of the biggest body-language mistakes job seekers make include failing to make eye contact, failing to smile, and bad posture.

Nervous habits like jingling your keys, shaking your leg, and scratching your head can also be construed as boredom, Randall says.

"Interviews are highly stressful, even for those doing the interviewing," Oliver says. "Through your body language, try to convey how delighted you are to be given the opportunity to compete for the amazing job."

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Embellishing

In a recent CareerBuilder survey, 69% of employers said that catching a candidate lying about something is an instant deal breaker, Haefner says.

"Lying or exaggerating during the hiring process can destroy your chances of ever being hired with that employer," she says. "And because of extensive background checks and references that come into play before an offer is made, it's easier to be caught than you might think."

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Being too eager

Asking, "How did I do?" or "Did I get the job?" projects eagerness that bridges on desperation and neediness. It's one thing to be excited about a job prospect, but you don't want to appear too hungry.

What's more, these kinds of questions are just plain awkward, as they put the interviewer on the spot. You'd be better off following up about feedback after you are or aren't offered the job.

Checking out mentally

"Of course you want it to be over, but while you're there in front of the interviewer, you must work to stay mentally present," she says. "Interviewers know when you are not there mentally."

Your distraction during an interview translates as either inadvertent rudeness (you just don't come off as all that interested in the job) — or unfocused answers ( you're not really answering the questions asked).

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Not being gracious

As Business Insider managing editor Jessica Liebman writes, one of the biggest mistakes you can make when competing for a new job is not saying "thank you" after an interview.

"Whether we spent 30 minutes meeting in the offices, we Skyped because you're abroad for your junior spring semester, or we did a quick first-round phone interview, you should always follow up later that day or the following day to say thanks and reiterate your interest," Liebman says.

A few things happen when you don't send a thank-you email. The hiring manager assumes you don't want the job. They think you're disorganized and forgot about following up. And there is a much higher chance they'll forget about you.